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Bat
Since the links I posted before do not seem to work anymore, I've created a bundle derived from the syntax file at http://adamv.googlecode.com/svn/editors/e/bundles/...

You can download the new bundle here:
http://www.textasticapp.com/support/Batch.tmbundle...

Have a look at the manual to see how can you install it in Textastic:
http://www.textasticapp.com/v4/manual/lessons/How_..

Once you install it, the "Batch File" syntax should be automatically selected when you open .bat or .cmd files.
Sorry that it took me so long, but here it is.

I've created a TextMate bundle from the Sublime Text package which is compatible with Textastic.

You can download the bundle from here: http://www.textasticapp.com/support/Fountain.tmbun...

I've also adapted the themes that come with the Sublime Package:
http://www.textasticapp.com/support/FountainThemes...

Please follow the instructions in the manual to use it with Textastic:
http://www.textasticapp.com/mac/manual/lessons/How..
The problem, as you wrote is that FireBug itself is JavaScript-based, so it probably dies when there is an actual syntax error in other JavaScript code.

I'm not sure if iOS offers the means necessary to report JavaScript errors in a web view. iOS 7 might have brought something new in this area, but I'll have to look into it. 
Did you see the syntax definition list in the File Properties popover? It isn't divided into language categories though.
How are you using Firebug Lite? In the preview window, you can enable Firebug, but that is really only useful for inspecting elements because it is loaded after the page is loaded and JavaScript is already executed.

Did you try to reference it directly from your HTML as the first script as described on the Firebug Lite site? http://getfirebug.com/firebuglite#Stable
You can already add custom themes to Textastic. This is explained in the manual: http://www.textasticapp.com/v4/manual/lessons/How_...

The "Mac Classic" theme can be found here: https://github.com/kballard/textmate-bundles/blob/...
TextExpander had to change the mechanism that is used to exchange snippets with third party apps. See http://smilesoftware.com/blog/entry/important-chan...

Textastic doesn't use the latest TextExpander SDK yet, so TextExpander doesn't currently work in Textastic. It will be fixed in the next update.
I found the problem: when Textastic sees a setting dictionary that doesn't contain a name and scope, this is considered to be the global theme settings dictionary that defines things as the selection and caret color.

In line 368 ( https://github.com/mekwall/obsidian-color-scheme/b...) there is an empty dictionary. So Textastic ignored the real settings dictionary and used the empty settings dictionary from line 368 instead.

Remove lines 368 and 369 from the theme file and it works!